diff --git a/.circleci/config.yml b/.circleci/config.yml
index 57a91ae9406ca..f9c9b99bff547 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -232,7 +232,7 @@ commands:
             ls -l ~/cache/sysroot/include/emscripten/heap.h
             cat ~/cache/sysroot/lib/wasm32-emscripten/crtbegin-mt.o.ccache-log
             date
-            cat ~/cache/build/libclang_rt.builtins/absvdi2.o.ccache-log
+            cat ~/cache/build/wasm32-emscripten/libclang_rt.builtins/absvdi2.o.ccache-log
             ccache -s
             ccache --print-stats
             ccache -p
diff --git a/tools/cache.py b/tools/cache.py
index c90b0d38acdbb..c182943cbc046 100644
--- a/tools/cache.py
+++ b/tools/cache.py
@@ -109,15 +109,13 @@ def get_sysroot_dir(*parts):
   return str(Path(get_sysroot(absolute=True), *parts))
 
 
-def get_lib_dir(absolute):
+def get_lib_dir_relative():
   from .cmdline import options
 
-  ensure_setup()
-  path = Path(get_sysroot(absolute=absolute), 'lib')
   if settings.MEMORY64:
-    path = Path(path, 'wasm64-emscripten')
+    path = Path('wasm64-emscripten')
   else:
-    path = Path(path, 'wasm32-emscripten')
+    path = Path('wasm32-emscripten')
   # if relevant, use a subdir of the cache
   subdir = []
   if options.lto:
@@ -132,6 +130,11 @@ def get_lib_dir(absolute):
   return path
 
 
+def get_lib_dir(absolute):
+  ensure_setup()
+  return Path(get_sysroot(absolute=absolute), 'lib', get_lib_dir_relative())
+
+
 def get_lib_name(name, absolute=False):
   return str(get_lib_dir(absolute=absolute).joinpath(name))
 
diff --git a/tools/ports/__init__.py b/tools/ports/__init__.py
index 8ae3d8ab1e5e9..819503125eff8 100644
--- a/tools/ports/__init__.py
+++ b/tools/ports/__init__.py
@@ -285,7 +285,7 @@ def erase():
 
   @staticmethod
   def get_build_dir():
-    return system_libs.get_build_dir()
+    return cache.get_path('build')
 
   name_cache: set[str] = set()
 
diff --git a/tools/system_libs.py b/tools/system_libs.py
index 9d082585abed9..d105e951f98ed 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -15,6 +15,7 @@
 import textwrap
 from enum import IntEnum, auto
 from glob import iglob
+from pathlib import Path
 from time import time
 
 from . import building, cache, diagnostics, shared, utils
@@ -84,7 +85,7 @@ def get_base_cflags(build_dir, force_object_files=False, preprocess=True):
 
 
 def get_build_dir():
-  return cache.get_path('build')
+  return cache.get_path(Path('build', cache.get_lib_dir_relative()))
 
 
 def clean_env():
@@ -179,6 +180,7 @@ def run_ninja(build_dir):
 def ensure_target_in_ninja_file(ninja_file, target):
   if os.path.isfile(ninja_file) and target in read_file(ninja_file):
     return
+  utils.safe_ensure_dirs(os.path.dirname(ninja_file))
   with open(ninja_file, 'a', encoding='utf-8') as f:
     f.write(target + '\n')